Nickel depositing bath and method



Patented June 20, 1944 2,351,966 NICKEL nnrosrrme BATH AND METHODGeorgeB. Hogaboom, New Britain, Conn, assignor to Hanson-VanWinkle-Munning Company, Matawan, N. J a corporation of New Jersey NoDrawing. Application October 12, 1940,

' Serial No.'360,918

6 Claims. (Cl. 204-49) This invention relates to the electrodepositionof nickel.

Among the objects *"of the invention are the provision of a bath andoperating conditions which will enable the deposition of the nickelat ahigh current density and consequent rapidity, to obtain a fine grainstructure of good color and to produce a deposit of a high degree ofductility.

The electrolyte, according to my invention, consists essentially of anaqueous solution of a nickel salt of a strong acid (hydrochloric acid),a nickel salt of a weak acid (acetic acid), and a sufiicient quantity ofthe strong acid (hydrochloric acid) to adjust the pH value of thesolution to the desired range. In general, the total nickelconcentration may vary from about 4.5 to about 17.0 oz./gal., and theratio of nickel from chloride to nickel from acetate may vary from 4.0to 12.0 oz./gal. nickel from chloride to 0.5 to 5.0 ozJgal. nickel fromacetate. A particularly favorable bath concentration is about 7.5 to10.0 oz./gal. of total nickel, of which from 4.0 to 5.0 oz./gal. issupplied-by nickel chloride and from 3.5 to 5.0 oz./gal.is supplied bynickel acetate. Experiments conducted by me have shown an importantcooperative effect of the particular bath ingredients employed. Aqueoussolutions of nickel chloride alone offer good electrical conductivity,but usually produce hard, brittle deposits. Agueous solutions of nickelacetate show a relatively poor conductivity and are easily decomposed byhydrochloric acid in quantities necessary to adjust the pH value of thebath. The performanceof a bath in which nickel chloride, nickel acetateand hydrochloric acid are all present in the proper proportions, is.such as to strongly indicate that an important and favorable interactionoccurs between the bath components, as a result of which the bath ,isremarkably free from hydrogen evolution at have been made in a bathcontaining 8.5 oz./gal.

total nickel, supplied in equal proportions by of about 130 F. Theresistivity of such a bath at 130 F. was found'to be about 8.75 ohms/c.c. at the pH value of 4.5. The resistivitytends to decrease at highertemperatures and lower pH values. The anode. efliciency and the cathodeefficiency were found to be 90% or better, and

' the bath composition and pHvalue were observed to remain approximatelyconstant, with rolled nickel anodes of about twice the, area of thecathode, over a long period of use. This particular bath composition ispreferred over other concentrations and ratios of components,

because of the particularly favorable operating conditions and the widerange of current densities over which the deposit remains of good color,semi-bright and ductile.-

The operating temperature for any of the bath compositions accordingtomy invention may be anywhere from room temperature to below'the boilingpoint, but the temperature range of to is considered'most practical forcommercial use.

Light, semi-bright, ductile deposits have been' obtained from bathscontaining 12.0 oz./ga1.

cient hydrochloric acid to adjust the pH value of the bath to 4.65 to5.00. Likewise, such deposits have been obtained at 10 to. 35 amps./sq.ft. of cathode surface in baths containing 4.2 oz./gal. nickel fromchloride and 0.5 oz./gal. nickel from acetate, with suflicienthydrochloric acid to adjust the pH value to 4.55. At a pH value from 1.0to 4.0, this bath gave a light matte, ductile deposit over a somewhatwider range of current densities, but the cathode efiiciency isgenerally low and the resistivity nickel chloride and nickel acetate,with, sufilcient concentrated hydrochloric acid to adjust I the pH valueof the bath to the range of 4.0 to 5.5 electrometric and operated at atemperature high. These observations were obtained at a temperaturein'the neighborhood of 130 F. At I pH values below 2.0 there is a.marked tendency in many of the baths for instability and decompositionof the acetate to occu'nand I con-' sider the useful range of .pH to bebetween 2.0 and 5.5 in most respects, such as the character of thedeposit and the. stability and operating conditions of the bath.

ing so small a quantity of nickel acetate are not nearly so favorable asthose in which greater quantities of nickel acetate are present. on theother'hand, it has also been observed that the operating conditions arenot quite so favorable when the quantity nickel from acetate is insubstantial excess of the nickel from chloride.

- In general, a. bath in which the nickel is supplied the nickel acetateshould constitute a substan-..

While some tial proportion of the electrolyte. other acetatesalt mightserve the function of a buffer, and salts of other metals than'nickelandacids other than those employed according tomy invention might serveto increase the conductivity of the bath, it is believed to be importantfor 'the proper action of my bath to avoid such substitutes for any ofthe components of the bath specified by me. Alkali metals and theirsalts are particularly objectionable as giving rise to decomposition ofwater and secondary deposition at the cathode, with consequentimpairment of the physical character of the nickel deposit. In otherwords, the invention contemplates a bath in which there is a common ioneffect due to the nickel'from the two sources (nickel chloride andnickel acetate) and a common ion effect from the chloride radical of thetwo sources and nickel acetate adjusted by hydrochloric acid to a pHvalue within the r'ange'o! 4.0 to 5.5 elec- (nickel chloride andhydrochloric acid), so that the ionization of the nickel chloride issomewhat depressed by the chloride ion of the hydrochloric acid, withconsequent increase in the ionization of' the nickel acetate.

I claim:

1. A nickel depositing bath consisting essentially of an aqueoussolution of nickel chloride and nickel acetate adjusted by hydrochloricacid to a pH value within the range of 2.0 to 5.5 elecnickel acetate.

I 2. A nickel depositing bath consisting essentially of an-aqueoussolution of nickel" chloride troinetric, the total nickel content of thebath being within the range of about 7.5 to 10,0 oz./gal.,

of which from about 4.0 to 5.0 oz./gal are sup- 3. A nickeldepositing'bath consisting essen- 'tially of an aqueous solution ofnickel chloride and nickel acetate adjusted by hydrochloric acid to a pHvalue in the neighborhood of 4.5 electrometric, the total nickel contentof the, bath being approximately 8.5 oz./gal., ,of which approximatelyequal proportions are .supplied by the nickel chloride and the nickelacetate.

4. A method of electrodepositing nickel, which comprises passing anelectrolyzing current from an anode to a cathode through' an electrolyteconsisting essentially of an aqueous solution of nickel chloride andnickel acetate, with sumcient hydrochloric acid to adjust the acidity ofthe bath to a pH value within the range of 2.0 to 5.5, the total nickelcontent of the bath being within the range of 4.5 to 1'7.0 oz./gal., ofwhich at least 4.0 oz ./gal. are supplied by nickel chloride and atleast 0.5 oz./8al. are supplied by nickel acetate. i

5. A method of electrodepositing nickel, which comprises passing anelectrolyzing current from an anode to a cathode through an electrolyteconsistingessentially of an aqueous solution of nickel chloride andnickel acetate, with sufllcient hydrochloric'acid to adjust the acidityoLthe bath to a pH value within the range oi 4.0'to 5.5, the totalnickel content of the bath being from 4.5 to 17.0 oz./gal., of which atleast 4.0 (m/gal. are supplied by the nickel chloride and at least 3.5oz./gal. are supplied by the nickel acetate.

6. The method of electrodepositing nickel, which comprises passing anelectrolyzing current from an anode to a cathode through an electrolyteconsisting essentially of an aqueous solution ot nickel chloride andnickel acetate, with sufllcient hydrochloric acid to adjust the acidityof the bath to a pH value in the neighborhood of 4.5, the total nickelcontent of the bath being-about 8.5 oz./gal. supplied in approximatelyequal proportions by the nickel chloride and the nickel acetate.

GEORGE B. HOGABOOM.

